Primary carcinomas induced in rats by 7-12 dimethylbenzanthracene (DMBA) or methylnitrosourea (MNU) contain alpha-LA quantities equal to the amounts found in the rat mammary gland during 1st to 2nd day of gestation. Among transplantatable tumors tested, only R3230 AC and MTW9 but not in DMBA #1, Ascites 13762 and MTW9A transplantable mammary carcinomas. Transplantation of a pituitary gland under the kidney capsule of the host (a) increased alphaLA content of primary DMBA induced mammary carcinomas, (b) reduced alphaLA content of primary MNU induced mammary carcinomas and (c) was unable to modify the alphaLA levels in 5 transplantable mammary carcinomas.